Injectable implants are currently used to bulk or augment tissues in medical applications ranging from vocal cord reconstruction, fecal and urinary incontinence, through to aesthetic treatments for wrinkles. Current implants are made from a range of materials including hyaluronic acid, proteins such as collagen, polymers such as polylactic acid and biomaterials such as hydroxyapaptite.
For example, hyaluronic acid (“HA”), sometimes referred to as hyaluronan or hyaluronate, is a naturally occurring mucopolysaccharide found in, for example, synovial fluid, vitreous humor, blood vessel walls and umbilical cord, and in other connective tissues. The polysaccharide consists of alternating N-acetyl-D-glucosamine and D-glucuronic acid residues joined by alternating β-1-3 glucuronidic and β-1-4 glucosaminidic bonds. Hyaluronic acid based products are cross-linked using a variety of approaches including, e.g., chemicals such as BDDE and divinylsulfane. The cross-linking hyaluronic acid is then micronized to enable injection (e.g., Restylane® and Juvéderm®). The hyaluronic acid implants produce their effect by bulking tissue and retaining moisture in the implant and are slowly resorbed by the body.
Another example is collagen based implants which have been based on collagen extracted from animal or human tissues, further cross-linked (e.g., glutaraldehyde (Zyplast®) or ribose based cross-links (Evolence®)) homogenised and then suspended in saline ready for implantation. Collagen implants produce their effect by bulking tissue in a similar way to hyaluronic acid products; however, they also allow greater cellular infiltration into the implant and production of nascent collagen material.
Approaches using polymers such as polylactic acid (e.g., Sculptra®) and biomaterials such as hydroxyapatite (e.g., Radiesse®) have been based on producing a suspension of particulate material in an injectable gel, typically a polysaccharide such as hyaluronic acid or carboxymethyl cellulose. Particulate implants produce their effect by inducing a foreign body response to the particles which leads to fibroblast encapsulation of the particles and collagen production—bulking the tissue through further tissue build up.
One problem with the current approaches to tissue bulking agents is that they do not enable the delivery of biomaterials which are based on or incorporate full length proteins or substantially full length proteins. Formulations which are based on or incorporate full length, or substantially full length, protein material, similar to those found naturally in the body, are more likely to retain the levels of biocompatibility and self recognition desirable for many of the intended applications. The process of chemical cross-linking typically leads to substantial intra-molecular cross-links which may disrupt the natural structure of the molecule; the micronization or homogenisation techniques used to enable product injection are not conducive to maintaining a full length, or substantially full length, protein molecular structure. In addition, the chemical cross-linking agents used to cross-link hyaluronic acid and proteins have known toxicity and may cause irritation, inflammation or carry carcinogenic risks.
The present disclosure is directed, in part, to providing injectable formulations of coherent biomaterials which are based on or derived from proteins, and enable the incorporated protein residues to retain their full length, or substantially full length, structure, and also enable the protein residues to be protected from rapid resorption and/or breakdown due to, e.g., proteolysis. In addition, the present disclosure is directed in part to biomaterials based on, and derived from, full length, or substantially full length, proteins which are amenable to needle injection, retain a coherent structure, are sufficiently cross-linked to slow resorption in vivo or combinations thereof. In addition, the present disclosure is directed in part to biomaterials which are substantially devoid of toxic chemical cross-linking agents. The present disclosure also provides, in part, methods, systems and/or kits for the preparation and/or formulation of at least one cross-linked protein matrix, comprising at least one protein residue and at least one biomolecule cross-linking agent residue, wherein at least one protein molecule is cross-linked with at least one biomolecule cross-linking agent to form the cross-linked protein matrix. In addition, the present disclosure also provides, in part, systems and/or kits for the preparation and/or formulation of at least one cross-linked protein matrix, comprising at least one protein residue and at least one polysaccharide residue, wherein protein molecules, such as substantially full length protein molecules or full length protein molecules, are cross-linked with polysaccharide cross-linking agents to form the at least one cross-linked protein matrix. There is a need for the compositions, methods, systems and/or kits disclosed herein.